Method of preparing gravure printing surfaces



May 2, 195o R. MaCKAY 2,506,427

METHOD ,QF PREPARING GRAVURE'PRINTING SURFACES Filed'NOv. 16, 1946 v2sheets-sheet 2 HMI.

will.;

mln.

INVENTOR Mac'.

BY a

ATTORNEY Patented May 2, 1950 METHOD OF PREPARING GRAVURE PRINTINGSURFACES Robert MacKay, Louisville, Ky., assigner to Reynolds MetalsCompany, Richmond, Va., a corporation of Delaware Application November16, 1946, Serial No. '710,373

2 Claims. (Cl. 101-33) The present invention relates to gravureprinting, in which intaglio printing cylinders are employed, and theinvention relates particularly to the provision of printing members,particularly copper or other cylinders having etched surfaces with cellsor depressions which are variable in depth, so as to provide superiortone effects and detail in the printed image. The primary object of theinvention is to provide a method whereby the problem of mis-register inmulti-color printing is eliminated in the employment of gelatine as theresist for etching with variable depths in copper or similar printingsurfaces. My method eliminates the necessity for making a composite ofthe images on a positive form which is the practice now followed.

The method commonly used throughout the gravure printing industry totransfer a multicolor picture image to copper and etch this image toform a printing surface consists of the following steps:

(a) From the original .art work a continuous tone negative is made. Thisnegative is reversed into a positive image, or a series of positiveimages in the case of duplicate units. This positive image is eithercontinuous tone or screen image, or as in the case o-f the Dultgenprocess both continuous tone and screen positive are used; (b) from thepositive image a print is made on a gelatine coated paper known to thetrade as carbon tissue; (c) this printed carbon tissue is thentransferred by a squeegee method to the copper, and by immersion, orvother application of hot water, the backing paper usedl to support thegelatine is removed and the gelatine image developed; (d) when dry, thisdeveloped gelatine resist forms the base through which the image isetched into the copper, forming an intaglio printing surface.

There are several objections to the foregoing operation. No adequatemeans has been found to control the stretch and shrinking of the paperduring color printing operations. This is the chief cause of misregisterbetween color elements printed by successive impressions. Because ofthis gelatine coated paper, it has been impossible to use modern stepand repeat machines for the preparation of printing surfaces by theintaglio or gravure method.

In accordance with the present invention,V the positioning and printingof the positive image is accomplished pho-tographically with a highdegree of accuracy, the use 'of carbon tissue is eliminated and themodern step and repeat machine can be .used in the preparation ofprinting surfaces by the gnavure or intaglio process.

In the practice of my invention, the color separation negatives andpositives are made in the usual way, and then printed on a speciallyprepared plastic or metal plate on which has been previously coated thegelatin which will, after exposure, be directly transferred from theplate to the copper printing surface. At this stage, the printedgelatine forms the etching resist.

I employ metal or plastic plates of preferably about l0/1000 thickness,smooth finished on one surface and formed with two register holesdrilled or punched in the proper position. These register holes providethe means for later positioning the gelatin image in exact position onthe printing surface.

These plates are then coated with a suitable `substratum to overcomehalation of the printed image and to make stripping easily accomplishedduring transfer to the copper printing member, usually a cylinder, priorto etching. On this substratum a standard mixture of gelatin and pigmentis coated, using a whirler or other suitable means. This gelatine andpigment can be sensitized before coating, or the plates can be coatedand stored to be sensitized later. This plate on which the gelatinpigment has been coated eliminates any possible misregister due toshrinkage as in the case loi" carbon tissue. The plate can then receivethe image. For example, it can be placed in a conventional step andrepeat machine and accurately positioned duplicate prints of any numbermade. This would not be possible with .carbon tissue.

In the drawings, I have shown a transfer machine by which transfer ofthe printed gelatine from the metal or plastic plate may accurately beperformed.

Fig. 1 is a front elevation of the transfer machine;

Fig. 2 is a detail perspective View of the plateholding frame with itspressure roller, a plate being shown held thereby against the surface ofa printing roller which is` to receive the printed gelatine;

Fig. 3 is a side elevation of the machine;

Fig. 4 is a purely schematic View, being a section showing the pressureand printing rollers, and the gelatine plate therebetween to indicatethe stripping of the printed gelatine, the slide carrier for the platehaving been omitted from the view; and

Fig. 5 is a fragmentary elevation showing one side portion of the frameand its reception of a guide lug carried by the plate.

In the following description the plastic or metal plate carrying thegelatine-pigment layer will be termed the gelatine plate. Referring tothe drawings, I have shown a frame consisting of the base member l, sideframe members 2, and transverse connecting member 3. Mounted on theflanged front of each side frame member 2 is a slide 4 formed with abearing boss .4m for a transverse shaft 5 which carries a pressureroller 6 which may be of hard rubber.' Forwardly depending arms 4mm, onecarried by each slide 4, may be connected by la `oar 1, and to this barmay be connected the lowerV .endso-f chains 8 led over the idlersprockets 9 to counterbalance weights I9. The sprockets can be carriedon a shaft II (Fig. 3) held by bracket arms I2 carried by the side framemembers.

Each slide 4 carries. an upwardly .projecting screw I3 in such mannerthat the latter is held against .endwise movement. Each screw I3 passesthrough the aperture of a boss i4 carried by an appropriate one of thetwo brackets l2 and thence extends upwardly into a gear box I5 in whichis an internally threaded gear (not shown) into which is received one ofthe screws I 3. Any suitable driven means may be employed to rotateinternally threaded gears which will be held against endwise movementsand rotated u ends of compression rollers, are apertured hanger risers91: of frame members 2li which frame members may be held in parallelismby cross bars at their ends, suchas cross bar 205cm shown in Fig. 2. Theframemembers mayk directly abut the compression roller as in Fig. .2, ormay be held spaced therefrom as in Fig. Each frame member 29 is formedwith a horizontal flange 20w cut with a longitudinal V groove.

The gelatine plate 2! is formed with registration holes. as in itscorners, to receive pinsf2lzr on a slide carrier 21m. The slide carrierpreferably is formed at its lower side margins with longitudinal wedgeprojections to be received in the said guiding grooves of the frame.

The space between .the compression roller 6 and the flanges 20x of theframe members will be such as to admit the inner areaof the slidecarrier 2 and the gelatine plate through such space for free slidingmovement on the frame 20.

Below shaft 5 is a second shaft, 22, journaled in bearing bosses 23carried by the main frameZ. This shaftis quickly removable and has ,asquared or vkey connection with the hub of an independently mounted wormwheel 24 driven by a worm V25 on a shaft 26 driven by suitableconnections Shaft 22 can be driven by bevel transfer of the printedgelatine to the copper cylinder or other printing member may be rubbercement or any other suitable material of a nature to readily free thegelatine from its said carrying plate.

When the gelatine plate has been printed it is applied to theundersurface of the slide carrier ZI, and in exact registration becausethe pins 2I$c of the slide carrier will enter the registration holes ofthe gelatine plate, and the latter will be held in such manner that thegelatine faces the copper cylinder 28.

Water is applied to the surface of the copper cylinder precedingthedownward movement of .the pressure roller 5, by the instrumentalitiesabove described, until rm but controlled pressure is imposed upon thegelatine plate. This wetting of the copper cylinder plus the pressurecauses the printed gelatine to be stripped from the metal or plasticplate as it passes through the machine. As hereinabove described thislast operation is performed by rotation of shaft 22 and the coppercylinder itself.

The metal or plastic plates can be re-coated and used over again in thesame manner.

After the transfer of the printed gelatine pigment from its plate to thecopper cylinder, any trace of rubber cement is removed and developmentwith hot water may proceed in the usual way, and then the gelatineresist may be dried, followed by etching to complete lthe preparation ofthe printing surface on the copper cylinder.

Having thus described my invention, what I claim and desire to secure byLetters Patent is as follows:

1. A machine adapted for' transferring gelatine pigment layers fromcarrierV plates therefor'and to printing cylinders, which comprisesmeans for rotatively supporting a printing cylinder, means for rotatingsaid cylinder, a pressure roller overlying said cylinder, means forraising and lowering the pressure roller, a frame intermediate theroller and cylinder and formed with guideways, a carrier mounted on saidguideway for sliding movement in position to be directly engaged by theprinting cylinder, and registration pins on said carrier forregistration with apertures in a gelatine plate in such manner that thegelatine surface of the latter is held in contact with the printingcylinder.

2. A machine constructed in accordance with claim 1 in combination withscrews carrying the pressure roller, power means for rotating saidscrews, and power means for rotating the printing cylinder, the carrierhaving ribs received in channels formed in the frame, and the framehaving. co-axial .support with the pressure roller.

ROBERT MACKAY.

REFERENCES CITED The following references are of .record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,340,346 Horgan May 18, 19201,989,017 Neumann Jan, 22, 1935 2,030,731 Young Feb. 11, 1936 2,213,443Huck Sept. 3, 1940 2,240,737 Hannon May 6, 1941 2,320,352 Ericksson June1, 1943

